(Reuters) - Former U.S. amateur champions Ryan Moore, An Byeong-hun and Matthew Fitzpatrick are among 27 players who have earned full exemptions into next month's U.S. Open at Oakmont, the United States Golf Association said on Tuesday.

All 27 exemptions were awarded to golfers ranked in the world's top 60 this week, and those additions lift the number of fully exempt players to 78 for the year's second major.

American Moore, who won the U.S. amateur in 2004, is ranked 49th, South Korean An, U.S. amateur champion in 2009, is 26th and Englishman Fitzpatrick, winner of the 2013 U.S. amateur, is 44th.

The other players who earned U.S. Open exemptions via the world rankings include Thais Kiradech Aphibarnrat and Thongchai Jaidee, Spaniard Rafael Cabrera-Bello, South African Jaco Van Zyl, Welshman Jamie Donaldson and India's Anirban Lahiri.

The U.S. Open, to be played from June 16-19, will be held for a record ninth time at Oakmont Country Club in Oakmont, Pennsylvania. The most recent U.S. Open staged there was in 2007, won by Argentina's Angel Cabrera.

World number two Jordan Spieth will defend the title he clinched by one shot at Chambers Bay last year, after fellow American Dustin Johnson blew his chance to force a playoff by three-putting the last.